Apparatus for determining the duration of a transient effect



June 1-2, 1945. w, RICHTER 2,377,969

APPARATUS FOR DETERMINING THE DURATION OF A TRANSIENT EFFECT Filed June1, 1942 2 Sheets-Sheet l Z AVAW.

June 12, 1945.

w. RICHTER 2,377,969

APPARATUS FOR DETERMINING THE DURATION OF A TRANSIENT EFFECT 2Sheets-Sheet 2 Filed June 1 1942 HIGH SCREEN GRID VOLTAGE MED. SCREENGRID VOLTAGE Low SCREEN GRID VOLTAGE PLATE C URRENT PLATE VOLTAGE time.

Patented June 12, 1945 APPARATUS FOR DETERMINING THE DURA- TION OF ATRANSIENT EFFECT Walther Richter, Whitefish Bay, Wia, asslgnor toCutler-Hammer, Inc., Milwaukee, Wis., a corporation 0! DelawareApplication June 1, 1942, Serial No. 445,393 14 Claims. '(01. 161--15.2)

This invention relates to apparatus for determining the duration of atransient effect, and more particularly to an instrumentality formeasuring the duration of an arc obtaining between contacts in anelectric circuit when said contacts are separated to interrupt a currentwhich flows in said circuit.

An object of the invention is to provide an instrument for measuring theduration of an arc incident to the opening of a circuit carrying acurrent.

Another object of the invention is to provide an instrument of highaccuracy 'for measuring the duration of arcs.

Another object is to provide an instrument of the aforementionedcharacter which'has a minimum number of moving parts, whereby thetendency to introduce errors of a high order is reduced.

Another object is to provide an instrument of the aforementionedcharacter which is readily adjustable for measuring time intervals of awide range of magnitude.

Another object is to provide such an instrument which is self-contained,compact, and easily transportable. I

Another object is to provide such a measuring instrument which is easilymanipulated.

Other objects and advantages of the invention will hereinafter appear.

The invention provides for charging a condenser during the existence ofan arc with a current which remains substantially constant during theentire charging period, that is, during the period during which the arcexists. charge of the condenser and hence its final voltage is then alinear function of the charging To attain this object the condenser isconnected to a source of current in series with a tetrode or pentodetube. The plate current of such' a tube is substantially constant over awide range of plate voltages for constant screen grid voltage. In orderto control the tetrode so as to provide a constant plate current, theinvention provides for impressing on the tube-during the existence of anarc, a control grid voltage and a screen grid voltage which aresuflicient to cause the desired charging current to flow to thecondenser, the value of the current being regulated by adjustment of thescreen grid voltage.

Fig. 3 is a diagram illustrating the relation 1 between plate voltageand current of the tube for different screen grid voltages. It will benoticed that for any given screen grid voltage, the plate currentremains substantially constant for a wide The total a across the otherdiagonal.

- The two outside terminals of secondary winding range of plate voltagesabove a very low minimum.

To measure the charge of the condenser its voltage is measured at theend of the charging 'period, that is, at the end of the arcing period,

by impressing said condenser voltage on the grid of an electron tubewhose equivalent resistance varies with the grid voltage. The lattertube forms one branch of a Wheatstone bridge across one diagonal ofwhich is a constant direct current voltage, while a microammeter isconnected The bridge is normally balanced by impressing a fixed voltageon the grid of the tube to affect its equivalent res'istance so that nocurrent flows through the microammeter. If now the accumulation of acharge on the condenser varies the potential of the grid of the tube itsequivalent resistance increases and this unbalances the bridge andcauses a current to how in the microammeter, the current being directlyproportional to the voltage of the condenser which in turn'is a measureof the charging time. p

The accompanying drawings are illustrative of an embodiment of theinvention.

In the drawings, Figure 1 is a circuit diagram embodying the invention;

Fig. 2 is a front view of the instrument panel carrying the variousinstruments and operating switches, while Fig. 3 illustratesdiagrammatically the relationship between the plate voltage and theplate current for different screen grid voltages of a pentode tube asused in the present system.

My invention will now be described by referring first to Fig. 1. In saidfigure a transformer I supplies the energy for operating theinstruments. The transformer has a primary winding l"- connectablethrough a. switch 34 and a fuse 41 to a suitable source of alternatingcurrent voltage, and a center tapped secondary winding l l of thetransformer are connected to the anodes 2 of a full wave rectifier 2,which is also provided with a cathode 2 of any suitable type. Connectedbetween the center tap of the winding l and the cathode is a condenser 3of relatively large capacity for smoothing out the ripples in therectified direct current voltage whichsexists between said cathode andthe center tap. This voltage in the present case is preferablyapproximately 300 to 350 volts.

Connected across the terminals of the condenser 3 in series with eachother and in series with a resistor 4, are two voltage regulating tubes5 and 5. The tube 5 preferably has an operating voltage of 150 volts,and the tube 6 preferably has an operating voltage of 90 volts.Connected in parallel with the tube 5 and in series with each Otheraretwo resistors 1 and 8, which form two adjoining branches of aWheatstone bridge. The Wheatstone bridge is completed by a resistor 9and a screen grid tube It]; the resistor 9 and the screen grid tube l0,connected as a triode, being connected in series with each other and inparallel with the resistors 8 and 1, respectively. The screen grid tubeID has a cathode In, a control grid I, a screen grid 1, and an anode Hi.A microammeter H is connected between the common point of the resistors1 and 8 ,and the common point of the resistor 9 and the cathode 10,respectively. Microammeter I is paralleled by a resistor l2,controllable by a normally closed switch l3.

The switch, the operation of which is to be investigated by theinstrument, is designated by the numeral I4. The switch |4 controls thecurrent of a translating device. Included in the switch circuit is aresistor ii, the purpose 0! which will be explained hereinafter.

Connected to one terminal 42 of the switch- I4 is the cathode l6 of anelectron tube Ii, which is provided with an anode i5 and a control grid|6. The control grid |6 is connected, in series with a resistor i1 and abias battery l8 or other source of direct current voltage, to the secondterminal 43 of the switch H. The battery |8 has its positive polenearest to the grid |6.

A tube l8 has a cathode I8 which is connected to that terminal 4| 0! theresistor |5 which is farthest removed from the switch l4, and its grid|8 is connected to the terminal 42 of the resistor l5 connected'to thecontacts l4. The anode |8 of the tube |8 is connected with the anode I6of the tube I5, and both of said anodes are connected through a resistorl9 to the positive pole 20 of the regulated power supply,

represented by the joint terminal of the resistor .4 and the tube 5. Thecathode |5 is also connected to a bus bar 2|, which in turn is connectedto the center tap of the transformer secondary winding l representingthe negative pole of the direct power supply.

The system further includes a tube 22 which has two cathodes 22 and 22and two cooperating anodes 22 and 22 respectively. The cathode 22 andthe anode 22 are jointly connected to the anodes lG and I8 and thecathode 22 is connected to a bus bar 23, which in turn is connected tothe common terminal of the tubes 5 and 6. A pentode 24 having a cathode24, an anode 24,a control grid 24, a screen grid 24- and a suppressorgrid 24, has its cathode 24 connected to the bus bar 23, while its anode24 is connected to a group of condensers 21.

Connected in series with each other and between the bus bars 20 and 23are the adjustable voltage dividers 25 and 26, which are provided withmovable contacts 25 and 25*, respectively. Condenser group 21 comprisesa number of sections 21, 21, 21, etc., arranged for parallel connectionof any desired number of sections by a switch 21 and is inserted betweenthe anode 24 and the contact 25. The number of condenser sectionsincluded in the circuit determines the range of the instrument-suchrange being selected according to the nature of the test to be made.Provisions are made for shunting the condensers 21 by a milliammeter 28through a normally closed switch 29.

The anode 22 of the tube 22 is connected through a control switch 30(here shown as a normally closed pushbutton switch) to the control grid24. Connected in series between the control grid 24 and the bus bar 2|are resistors 3| and 32. The control grid 24 is connected throughresistor 3| to a voltage divider formed by resistors 32 and 33 which areconnected across bus bars 2| and 23.

Referring now to Fig. 2, the same illustrates an instrument which isconstructed and assembled in accordance with the diagram shown inFig. 1. The various elements of the system including the tubes,condensers, and resistors and switches aforedescribed are enclosed in acabinet 40 which is provided with the three terminals 4|, 42, 43, to beconnected to a switch to be tested in accordance with the diagram ofFig. 1.

On the front side of the cabinet is installed the dial 28 of themilliammeter 28. A second dial I is the dial of the microammeter Theswitch handle 34 is the operating handle of the line switch 34, andbelow this is mounted the fuse 41. The pushbutton 39 is adapted whendepressed to open the normally closed contacts of switch 30.

A rotating indicator 28 provided with a callbrated dial is connected tothe contact 26 01 the potentiometer 26. A knob 25 provided with acalibrated dial is connected to'the contact 25 of the potentiometer 25.An indicating knob 21' provided with a calibrated dial is connected tothe commutator 21 for commutating the condenser sections 21, 21*, etc. Apushbutton 49 is adapted when depressed to open the normally closedcontacts l3 and 29.

Referring again to Fig. 1 it will be noted that on account of therectifier action of the tube 22 current can only flow in the resistor 3|in a direction to increase the negative potential of the grid 24 withrespect to the cathode 24. The resistors 3|, 32 and 33 are soproportioned that said negative potential is of a value to render thetube 24 non-conducting.

The rectifier path 22 22 becomes conducting when the anodes 5 and l8tend to become positive with respect to the bus bar 23, thereby limitingthe swing of the positive potential of said anodes and preventing delayin response of the tube 24. The cathode 22 is connected to the resistorI9, which is the common load resistor of the tubes I6 and I8 The tube Itis normally conducting, but is rendered non-conducting when its grid |6is made negative with respect to its cathode |6; that is, when there isa voltage drop across the contacts |4, exceeding the voltage of thebattery l8, with a polarity making 43 negative with respect to 42. Onthe other hand, the tube H3 is non-conducting if a voltage drop existsin the resistor l5. This takes place even with switch |4 open when anarc maintains current flow in the load circuit. The tube |5 responds ina similar manner to the voltage across the switch [4. The time duringwhich an arc exists between the contacts I4 is therefore characterizedby the simultaneous stoppage of current through the tubes l6 and I9.When either tube I6 or l9 carries current, a current flows through theresistors 'It and 3|, the normally closed contacts of pushbutton switch30 and the anode 22 to cathode 22', through the respective tube It or l8to bus bar 2|. The flow of current through the tube 24. with the switch20 closed the charging current can be read on the milllammeter 28. Thebattery it insures a small positive potential to compensate for apossible voltage drop the switch l4 in its closed position, which dropmay render the grid l8 negative and stop current flow in tube l8 whennot desired.

To operate the instrument connections are made between terminals 4|, 42and 43 to the power circuit as indicated in the diagram, Fig. 1, wherebythe polarities are such that the terminal 4| is more positivethan-terminal 42 and the latter is more positive than terminal 43.Thevcltage drop of the resistor i should be between approximately 1 to 5volts. The several adiustments of the instrument should be made with theswitch 14 closed and preferably with no current flowing in the powercircuit. then closed and the cathodes of the various tubes are permittedto heat up to their normal temperatures. contact II should remainclosed. Thereafter the contact I3 is opened and the current passingthrough the tube I0 is adjusted by adjustment of the contact which underthese conditions regulates the potential of the grid ill". Theadiustment is made so that the instrument I i reads zero. In otherwords, the bridge is balanced by making the voltage drop across the tubeIn equal to the voltage dropacross resistor I.

Thereafter normally closed contacts of pushbutton switch are opened, bydepressing the latter, and the plate current of tube 24 is adjusted tothe desired point by moving contact 26* by means of the knob 26' (Fig.2); that is, so that a potential is impressed upon the grid 24 whichcorresponds to the desired value or current passed by the tube 24, ashas been explained heretofore. Thereafter the contact 21 is adjusted byknob 21 (Fig. 2) to connect the desired number or condenser sections inparallel. The condenser sections are preferably of equal capacity, sothat the voltage rise of the condenser for a given charging period isinversely proportional to the number of sections connected in circuit.On the other hand, it will also be obvious that the voltage rise of thecondensers is directly proportional to the product of the constantcharging current and the charging time.

If it is desired to determine the duration of an are on the switch l4,the switch 30 is closed and the switches 29 and I3 are opened. It nowthe contact l4 opens, a charging current will flow to the section orsections of condenser group 2'! as long as the arc persists, as has beenexplained heretofore. This raises the voltage of the active sections ofthe condenser group 21 at a constant rate, and thus the potential of thegrid Ill varies the current flow through the tube l0 and the instrumentI I, until at the moment of interruption of the arc, the deflection ofthe instrument II is a maximum and this maximum deflection, whichpersists as long as the active condenser sections 21, 21, etc., are notmeasurably discharged, is

. a direct measure of the total energy stored in the active condensersections, and as the latter were charged at a constant current, thedeflection is also a measure or the time during which the arc persisted.

Should the voltage of the arc be too high for direct application to thegrid 16, a suitable voltage divider may be inserted in the circuit in awell known manner.

The switch 34 is During the heating-up period the The instrument mayalso be used to measure the time of other transient conditions, such asa transient voltage or current in a circuit. For such measurements it isoften only necessary to employ one or the tubes It or It.

a I claim:

1. In apparatus for determining the duration of a transient eifect, thecombination with a first electron tube having a cathode, an anode and agrid, of means to impress a voltage resulting from a characteristic ofsaid transient eflect-upon said grid to vary the current flowing in saidtube, a condenser, a second electron tube in circuit with said condenserand having a grid and adapted to maintain a substantially constantcurrent flow therethrough, means to supply current to said second tubeand said condenser, means to impress a voltage resulting from thevariations or current flowing in said first electron tube upon the grid0! said second tube to render said second tube conducting and to chargesaid condenser with a constant current, a third electron tube having acathode, an anode and a grid, means to connect the cathode and anode ofsaid third tube to a source of current, a connection between saidcondenser and said last named grid for impressing the voltage oi! saidcondenser upon the grid of said third tube, and means to measure thecurrent in said third tube resulting from the potential impressed uponthe grid thereof.

2. In apparatus for determining the duration of a transient effect, thecombination with a first electron tube having a cathode, an anode and agrid, of means to impress a voltage resulting from a characteristic ofsaid transient effect upon said grid to vary the current flowing in saidtube, a variable condenser, a second electron tube in circuit with saidcondenser and having a first grid and adapted to maintain asubstantially con- 40 stant current flow therethrough, said second tubealso having a second grid adapted to vary the magnitude or said current,means to supply current to said second tube and said condenser, means toimpress a voltage resulting from variations of the current flowing insaid first tube upon said first grid of said second tube to render thelatter conducting and to charge said condenser with a current inaccordance with the potential impressed upon said second grid of saidsecond tube, a third electron tube having a cathode, an anode and agrid, means to connect the cathode and anode of said third tube to asource of current, means to impress the voltage of said condenser uponthe grid oi'said third tube and means to measure the current in saidthird tube resulting from the potential impressed upon the gridthereof.

3. In apparatus for determining the duration of a transient effect, thecombination with a first electron tube having a cathode, an anode and agrid, of means to impress a voltage resulting from a characteristic ofsaid transient effect upon said grid to vary the current flowing in saidtube, a condenser, a second electron tube in circuit with said condenserand having a grid and adapted to maintain a substantially constantcurrent flow therethrough, means to supply current to said second tubeand said condenser, means to impress a voltage resulting from variationsof the current flowing in said first electron tube upon the grid of saidsecond tube to render said second tube conducting and to charge saidcondenser, a

'third electron tube having an anode, a cathode and a grid, threeresistors, each of said resistors and said third tube forming one of thefour sides of a normally balanced Wheatstone bridge,

means to impress a potential across one diagonal of said Wheatstonebridge, and means to measure a grid, of means to impress a voltageresulting from a characteristic of said transient effect upon said gridto vary the current flowing in said tube, a condenser, a second electrontube in circuit with said condenser and having a first grid which tendsto maintain a substantially constant current fiow therethrough, saidsecond tube also adapted to maintain a constant current flowtherethrough, said second tube also having a. second grid, means toimpress an adjustable potential upon said last mentioned grid to therebyvary the magnitude of said current, means to supply current to saidsecond tube and said condenser, means to impress a voltage resultingfrom the variations of current flowing in said first electron tube uponthe first grid of said second tube to render the latter conducting andto charge said condenser with a constant current,

' and means for measuring the total charge of said having a second gridadapted to vary the magnitude of said current, means to supply currentto said second tube and said condenser, means to impress a voltageresultin from the variations of current flowing in said first electrontube upon the first grid of said second tube to render the latterconducting and to charge said condenser with a current in accordancewith the potential impressed upon the second grid of said second tube, athird electron tube having an anode, a cathode and a grid, threeresistors, said resistors and said third tube each forming one of thefour sides of a normally balanced Wheatstone bridge, means to impress apotential across one diagonal of said bridge, and means to measure thepotential across the other diagonal of said bridge resulting from anunbalance thereof by the change in current fiow through said third tubein response to the voltage impressed upon its grid by said condenser.

5. In apparatus for determining the duration of a transient effect, thecombination with a first electron tube having a cathode, an anode and agrid, of means to impress a voltage resulting from a characteristic ofsaid transient effect upon said grid to vary the current flowing in saidtube, a variable condenser, a second electron tube in circuit with saidcondenser and having a first grid and adapted to maintain asubstantially constant current flow therethrough, said second tube alsohaving a second grid, means to impress an adjustable potential upon saidlast mentioned grid to thereby vary the magnitude of said current, meansto supply current to said second tube and said condenser, means toimpress a voltage resulting from variations of the current flowing insaid first tube upon the first grid of said second tube to render thelatter conducting and to charge said condenser with a current inaccordance with the potential impressed upon the second grid of saidsecond tube, a third electron tube having a cathode, an anode and agrid, means to connect the cathode and anode of said third tube to asource of current, means to impress the voltagee of said condenser uponthe grid of said third tube, and means to measure the currentv flowingthrough said third tube as a result of the potential impressed upon thegrid thereof.

6. In apparatus for determining the duration of a transient effect, thecombination with a first electron tube having a cathode, an anode and agrid, of means to impress a voltageresulting from a characteristic ofsaid transient effect upon said grid to vary the current flowing in saidtube, a condenser, a second electron tube in circuit with said condenserand having a first grid normally condenser.

7. In apparatus for determining the duration of an arc, the combinationwith a condenser for accumulating a charge, of means responsive to thecurrent and the voltage of said arc including means to supply asubstantially constant charging current to said condenser, and means formeasuring the total charge. of said condenser.

8. In apparatus for determining the duration of an arc, the combinationof a condenser tor accumulating a charge, means responsive individuallyto the voltage and to the current of an are including means to supply asubstantially constant charging current to said condenser during theexistence of an arc, and means for measuring the terminal voltage orsaid condenser result. ing from said charging current.

9. In apparatus for determining the duration of an arc, the combinationwith a condenser, of an electron tube connected to respond to thevoltage of said arc, a second electron tube connected to respond to thecurrent of said arc, a third electron tube having a cathode, an anodeand a grid connected in circuit with said condenser and adapted tomaintain a substantially constant current flow therethrough, means tosupply current to said electron tubes, means to impress the current ofsaid first and said second tubes upon the grid of said third tube torender the latter conducting and to charge said condenser, and means formeasuring the total charge of said condenser. v

10. In apparatus for determining the duration of a transient effect, thecombination with an electron tube provided with a first and a secondcontrol grid, and adapted to pass a current substanstantiallyindependent of the voltage impressed upon said tube, of currentresponsive means connected in circuit with said tube, means to connectsaid tube to a current source, means arranged to normally impress uponsaid first grid 9. potential rendering said tube non-conducting, saidmeans being responsive to a characteristic of a transient to modify saidpotential and render said tube conducting and supply a constant currentto said condenser, and means to impress upon said second control grid apotential adapted to vary the current passing through said tube inaccordance with the magnitude of said last named potential.

11. In apparatus for determining the duration of a transient effect, thecombination with an electron tube provided with a first and a secondcontrol grid, and adapted to pass a current substantially independent ofthe voltage impressed upon said tube, of a condenser connected incircuit with said tube, means to connect said tube and said condenser toa source of current for charging said condenser by the current passed bysaid tube, means arranged to normally impress upon said first grid 9.potential rendering said tube non-conducting, said means responding to acharacteristic ofa transient to modify said potential and render saidtube conducting and supp y a constant current to said condenser, meansto impress upon said second control grid a potential adapted to vary thecurrentpassing through said tube in accordance with the magnitude ofsaid last named potential, and means to measure the volt age of saidcondenser resulting from the current passed by said tube.

12. In apparatus for determining the duration of a transient effect, thecombination with a first electron tube provided with a first anda secondcontrol grid, and adapted to pass a current substantially independent ofthe voltage impressed upon said tube, of a condenser connected incircuit with said tube, means to connect said tube and said condenser toa source of current for charging said condenser by the current passed bysaid tube, means arranged to normally impress upon said first grid apotential means to impress the voltage of said condenser upon the gridof said second tube, and means to measure the current flowing throughsaid second tube as a result of the potential impressed upon the grid ofsaid second tube.

13. In apparatus for determining the duration of an arc, the combinationwith a condenser for accumulating a charge, of means responsive to atleast one characteristic of said are and arranged to supply asubstantially constant charging current to said condenser in response tovariations of said characteristic, and means for measurin the totalcharge of said condenser.

14. In apparatus for measuring the period of simultaneity of twocharacteristic physical quantities of a system, the combination of afirst and a second electron tube each having a cathode, an anode, and agrid, means to impress upon the grid of one tube a, voltage controlledby one 01 said quantities and upon the grid of the other tube a voltagecontrolled by the other quantity to thereby vary the values of thecurrents flowing in the respective tubes, a condenser, a third electrontube in circuit with said condenser and having a first grid adapted tomaintain a substantially constant current flow therethrough, said thirdtube also having a, second grid adapted to vary themagnitude of saidcurrent, means to supply current to said third tube and said condenser,means to impress upon said second grid of said third tube a constantvoltage which is controlled by the output currents of said first andsecond tubes to render said third tube conducting and to charge saidcondenser with a constant current, and means to measure the charge ofsaid condenser.

WALTHER RICHTER.

